When asked by Business Insider, YouTube said the clarification had not been prompted by any specific internet challenge and that it had been in the works for months. A spokesman said:

"YouTube has long prohibited videos which promote harmful or dangerous activities and we routinely review and update our enforcement guidelines to make sure they're consistent and appropriately address emerging trends.

"We heard feedback from creators that we could provide some clarity on certain Community Guidelines, so we published materials detailing our policies against pranks that cause others to seriously fear for their safety or that cause serious emotional distress to children and vulnerable individuals."

In its FAQ post, YouTube told creators that they have a two month "grace period" in which to clean up their channels of any offending content, during which time YouTube will remove videos but not hand out strikes to channels. Strikes are warnings to users - if they get too many in a short period of time, YouTube terminates their account.

A cursory search of YouTube shows the scale of the task it faces in keeping stunt videos under control. Searching for the "Bird Box" challenge brings up countless results, while it also appearing among suggested search terms.

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